Security alarm system



Oct. 17, 1961 K. H. SCHMIDT 3,005,191

SECURITY ALARM SYSTEM Filed July 1o, 1957 2 Sheets-Sheet 1 lil CE-CoA/mm nv/7' l x u nu manana 1| N N Y \Uumununn iv N t uu L f l Si l IINVENTOR M ae, 505ML,

BY 6K.

ATTORNE Oct. 17, 1961 K. H. SCHMIDT SECURITY ALARM SYSTEM 2 Sheets-Sheet2 Filed July l0, 1957 3,005,191 SECURITY ALARM SYSTEM Kenneth H.Schmidt, Danbury, Conn., assigner to Mosler Research Products, Inc.,Danbury, Conn., a corporation of Delaware Filed .iuly 10, 1957, Ser. No.670,999

Claims. (Cl. 340-258) My invention relates broadly to electronicsecurity alarm systems, and more particularly to a transistorized,capacity-type alarm system, with an automatic self-supervisory circuitfor non-operating periods of the alarm system.

.One of the objects of my invention is to provide a capacity-type alarmsystem which provides protection and electronic supervision of theconnecting lines between system units during non-operating periods ofthe capacity alarm system.

Another object of my invention is to provide a supervisory circuit forthe connecting conductors between system units which is automaticallyswitched into operation when the oscillator and resonant antennacircuits of the capacity-type alarm system are deenergized.

Another object of my invention is to provide a capacity-type alarmsystem in which the connecting lines between system units are under theconstant supervision of an ultra-sensitive alarm producing relay duringoperating periods of my capacity-type alarm system.

Another object of my invention is to provide a capacity-type alarmsystem which goes into an alarm condition whenever the system is turnedon, to notify the guard at the remote surveillance station that the areais ready to be secured.

Another object of my invention is to provide a capacity-type alarmsystem which goes into an alarm condition whenever the system is turnedoff in order to prevent unauthorized deenergizing of the system.

Another object of my invention is to provide a compact, self-powered,transistorized capacity-type alarm system.

A further object of my invention is to provide a capacity alarm systemin which the components of the oscillator, antenna tuning, and detectorcircuits are under constant electronic surveillance in order to preventany unauthorized tampering with the components of said circuits.

Other and further objects of my invention are set forth more fully inthe specification hereinafter following by reference to the accompanyingdrawings, in which: i

FIG. l is a simplified block diagram in schematic arrangement of mycapacitance-type alarm system;

FIG. 2 is a perspective view of a typical installation of the capacityalarm system of my invention and particularly showing the constructionof the antenna system and the manner in which a'multiplicity ofprotected areas may be electronically observed at a remote centralstation;

FIG. 3 is an overall electrical schematic diagram of the capacity-typealarm system ofmy invention.

My invention is directed to the construction of anrelectronic securityalarm system. in which the objects under 'i States Patent O ICC 2 neticfield will upset the balance of the relay circuit thus sending in analarm since the amount of RF energy stored inthe iield has been changed.

The antenna resonating circuit is tuned so that any unauthorizedtampering with the connecting lines between system units duringoperatingperiods will cause a current change in the balanced relay circuit thusthrowing the alarm relay and initiating the alarm.

Whenever the system is turned on or oil there is a current change in thebalanced relay circuit .of sutlicient magnitude to cause the alarm to beinitiated due to the system imbalance thus created.

Y During non-operating periods `of the alarm system, that is, when theoscillator and antenna system circuits are deenergized, an independentsupervisory circuit is `automatically switched into the system whichby-passes the oscillator, antenna tuning, `and detector circuits andimpresses a voltage across the connecting lines between the systemunits. Any tampering with the connecting line while the system vis inthis mode of operation will change the current `to the balanced alarmrelay circuit and cause an ammeter installed in that circuit to indicatean unbalanced condition. 'I hus the connecting lines `between the unitsof the system are under protective sur` veillance during both operatingand non-operating periods of the antenna system. This is also true ofthe oscillator, antenna tuning, and detector circuits since the housingin which `they ,are encased is associated with a tamper switch which isin series with one of the connecting lines.

In referring `to the drawings in more detail, similar numerals refer .tosimilar components throughout this specification.

In FIG. A 1 I have shown the basic block diagram of my capacity alarmsystem. ',It consists of: control unit 1; guard `unit 2; and theobjects, assembly, or area `to be protected designated by referencecharacter `It. Reference Acharacter 4 designates the antenna connectionline connecting the control unit 1 to the insulated object or area underprotection which forms the antenna system,

, .by transmitting radio'rrequency energy from control unit protectionare connected in series and form an antenna 'balanced for the particularantenna system and the prence of any additional body or object intheelectromag- 2a into an antenna system, comprised in this particularillustration, of conductor 4a; tile cabinets 7, 8 and 9; and .safe 10.The cabinets and safe are insulated from ground .by insulating blocks11and wired together at 12, 13, and 14 with heavy braid to complete theantenna circuit betweenthe objects. The system is `balanced for theparticularsafe and .file cabinets or other objects or area underprotection. ,Any additional object, such as a human being, .placed ,inthe sensitve area which entirely surrounds .the safe, will change theamount .of radio frequency energy stored in the field. This in turn willcause unbalance vin `the alarm unit 2a, which is: the guard unit .forzone A. i

This capacitance systemmay-be either a single system installation or amultiple system installation as .shown in EHS. 2. .Here i hare .shownthe guard units 2a, 2b, v2c and 2d of four separate systems installed ata common central station lto enable one guard to maintain electronicsurveillance over four separate removed areas.` Withthisyarrangernentkan intrusion in .one of the protected V3 Y areas willindicate an alarm at its associated central station guard unit, thuspin-pointing the area of intrusion so the guard knows exactly where totake immediate action. The systems are not associated in any mannerexcept that they may .usel a common guard unit` power Source.

I have shown the electrical wire schematic diagram of my invention inFIG. 3. The diagram is divided into two y.basic sections, the controlunit 1 and the guard unit 2.

The control unit is self-powered by one 1.5 volt dry cell type battery15 which supplies-B'- voltage for said unit. Because a transistor isutilized in the circuit rather than a vacuum tube, this one battery willoperate the system for approximately one year. The Day-Night switch 16-`is connected in series with the power supply conductor With switch 16in the Night position, B- through conductor 22, after being filtered bybypassca'pacitor -23, is suppressed on the transistor oscillator circuitwhich 7, 8, and 9, and safe 10 in FIG. 2). 'I'he antenna system is tunedor resonated by selecting the appropriate i tap on the primary oftransformer 29 and adjusting tuning capacitor 28 while observing tuningmeter 30 as an indicating means for such procedure. The circuit isktuned so that there is a small voltage across the secondary winding ofdetector transformer 29. The sensitivity of the antenna system can beincreased by changing the value of or removing desensitizing capacitor27.

`The detection circuit is comprised of the secondary winding oftransformer 29; blocking capacitor 31; a rectitier circuit consisting ofcrystal' dioder 32 connected to ground and crystal diode 33 connected inseries with Vthe detector output conductor 34; and by-pass capacitor' 3S'to ground o'n the output of diode 33. The remainder of the control unitcircuit consists of tuning meter 30 which is a micro-ampere meter, and.tamper switch 36 connected in vseries with output conductor 34. Tamperswitch 36 is positioned in the control unit in such a manner that itcompletes the control unit output circuit when the lcontrol unit housinglis in place while thesame circuit is opened when the control unithousing is'removed.

This is to prevent unauthorized tamperingwith the control unitcomponentsV as will be discussed later. Ground line 6 in the controlunit is grounded at the control unit.

Control unit output lines 34 and 6 arev connected to conductors 37 and6", respectively, in guard unit 2 by connecting lines and 6,respectively. Protection meter 38 is connected in series with conductor37 and is 'a duplicate to tuning meter 30. This meter is placed-in theguard unit so a guard at a remote location' is assured that everythingis in proper balance at the protected area, and no connecting lines,etc.,V have been tampered with. If one of the tile cabinets, etc., hadbecome disconnected or grounded during the Day period, the meter wouldnot read in the safe portion of the meter scale when switch 1,6 isswitched to the Night position. If the control unit housing or theconnecting lines 5 and 6 were tampered with while switch 16 is in theDay position the -meter would read in the unsafeportion of the scale butno change in meter indication will result from-tampering with theantenna system components while this switch is in the Day position. v

When switch 16 is switched to the Day position,'B- excitation is removedfrom the oscillator, circuit which .results in deenergizing the antennasystem and the detector circuit. B- is now applied to a supervisorycircuit vcontrol unit output current. manual reset alarm relay respondsto any change in curwhich provides for the protection and supervision ofthe control unit housing and the connecting lines during thenon-operating or Day periods of the alarm system. This supervisorycircuit is comprised of switch 16 in the Day position, voltage dropresistor 50 andrDay balance resistor 51, all in series with conductor 52which connects to detector .output conductor 34 between the junction ofcrystal diode 33 and by-pass capacitor 35, and tuning meter 30, thusinserting the supervisory circuit in series with tuning meter 30.

The principal portion of the guard unit circuit consists of the balancedalarm relay circuit which is composed of compensation capacitor 39 inseries with ultrasensitive alarm relay coil 40 shunted by load resistor411 and also b y by-pass capacitor 42. Movable contact arm 43 of themanual reset alarm relay is grounded. The alarm relay stationarycontacts `44 are connected to one end of slave relay coil 45 while theother end is connected to B+. Movable contact arm 46 of the slave relayis `connected to Bi-i- Two alarm signals connected in parallel areprovided at the guard unit, a buzzer 47 and a light 48. When the systembecomes unbalanced and goes into alarm both alarm signals will indi-.cate since slave Arelay contact control arm 46 impresses Bi-lacrosseach. The buzzer can be silenced by means of silencer switch 49 but thelight will not go out until .the system is rebalanced and operatingproperly. To

prevent the guard from foregetting to turn the buzzer back on, thesilencer switch must be returned to the normal operating position` whenthe unit is rebalanced or the buzzer alarm will indicate since in thisstate the slave relay contact arm 46 when it returns to its deenergizedposition impresses Bi-lacross the buzzer if the silencer switch has notbeen returned to its normal operating position. l

The light and buzzer indicators in the guard unit may .operate lfromvolts A.C. power with a 6 volt standby battery so arranged thatif theA.C. power supply vshould fail, all components of the guard unit wouldcontinue to operate without interrupt-ion since the stand-by `batterysupply would be switched into the circuit auto- .matically. With switch16 in the Night position a wouldbe intruder passing into or through theparticulararea under protection will change the amount of radiofrequency energy stored in the field by the antenna system, since thesystem is balanced for the particular area under protection. Thischanges the capacity of the antenna system and results in a change involtage across the secondary winding of transformer 29 and thus a changein The ultra-sensitive guard rent exceeding two micro-amperes, thus theabove current vchange activates the alarm relay coil 40 which results incoil 45 of the slave relay being activated and impressing B+. across thealarm indicators by means of slave relay movable contact 46.

Since there is always a small voltage present across the secondarywinding of transformer 29, if an unauthorized person opened the`control-unit housing the tamper switch 36 would break the outputcircuit, causing the 'current to drop to zero and this currentchangewould throw the alarm relay, and through the chain reaction setforth above, the alarm would be activated.

' The alarm will also be activated if the connecting lines between, thecontrol unit and the guard unit are cut, jumpered, or if the wire isbared and touched with the linger or a metal object, because eachchanges the current in the circuit sufficiently to instantly activatethe Aalarm relay.

I When the Day-Night switch is switched from Night to Day the oscillatoris deenergized; thus the voltage across the secondary of transformer 29disappears'so the alarm is activated from the resulting eurent change ordisap pearancegTrhis eliminates the possibilityV of an intruden turning.off the alarm system since such a move sets of@ the alarm. When itcomes time to operate the system in the Day position the switching-overprocess will activate the alarm and the guard athis remote locationbeing notified that it is an authorized system switch-over can manuallyreset the alarm relay thus deenergizing the alarms.

During Day position operation a B- D C. Voltage is impressed across theconnecting lines 5 and 6 and any cutting or breaking of such lines orany opening of the control unit housing will result in the metersceasing to indicate since they are in series with the tamper switch andconnecting lines. No alarm is activated in this state since compensationcapacitor 39 blocks the DC. voltage and thus makes the alarm relay coil40 insensitive to D C. current changes.

Since during Day operation the antenna system (i.e. safe, file cabinets,etc.) is not under protection the objects or area of the antenna systemmay be touched and used as they customarily are during the day. Anydamage to this section of the system during Day operation will not bediscovered until the system is switched to Night operation.`

When switch 16 in the control unit, which is located in the area underprotection, is switched to the Night position thecorresponding guardunit goes into alarm because of the current change from zero to somevalue. This notities the guard at the guard unit that the control unithas been switched into Night operation. If during Day operation someonehad purposely or accidentally damaged the system, such as breaking orcutting an antenna connection, grounding, or any break-down of internalcomponents of the control unit, meters Sti and 38 would indicate in thedanger zone, indicating a system unbalance. This would put the guard onnotice of a failure in the system which must be corrected bytroubleshooting If the guard unit meter indicates in the balanced zone,the guard at the guard unit secures the area by resetting the 'manualreset alarm relay, stopping the alarm and thus putting the system inoperation until such time as the sensitive balance is upset by somecause. No warning signal is audible or visible in the secure area sothat the ywould-be intruder setting olf the alarm does not know he hasinformed the guard of his presence.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is as follows:

l. An alarm system comprising a control unit disposed in the area to beprotected, a guard unit disposed in an area remote from the protectedarea, and two connecting lines electrically interconnecting said guardunit and said control unit, said control unit comprising a directcurrent power Source, an oscillator circuit, a manually operated switchhaving first and second operative positions, said switch when in saidrst position being effective to interconnect said power source and saidoscillator circuit, an antenna system connected to said oscillatorcircuit, an antenna tuning circuit connected with said antenna system, adetection circuit interconnected with said antenna system, the outputleads of said detection circuit being interconnected to said con nectinglines, a bypass line effective to interconnect said switch with one ofsaid connecting lines when said switch is in said second operativeposition, whereby when said switch is in said first position saidoscillator, said antenna system and said detection circuit are energizedand apply an alternating current signal to said connecting lines, saidsignal being modified upon any intrusion into the protected area, andwhereby when said switch is in said second position said oscillator isdeenergized and a direct current signal is applied from said powersource across said connecting lines which signal provides means at theguard unit for supervising saidV connecting lines, said guard unitcomprising an ultra sensitive balanced arm relay circuit energized fromsaid connecting lines, an alarm indicator energized in response to theactuation of said balanced arm relay, and indicating means responsive tocurrent flow through said connecting lines.

2. An alarm system comprising a control unit disposed in the area to beprotected, a guard unit disposed in an area remote from the protectedarea, and two connecting lines electrically interconnecting said guardunit and said control unit, said control unit comprising a directcurrent power source, an oscillator circuit, a manually operated switchhaving first and second operative positions, said switch when in said frst position being effective to interconnect said power source and saidoscillator circuit, an antenna system connected to said oscillatorcircuit, an antenna tuning circuit connected with said antenna system, adetection circuit interconnected with said antenna system, the outputleads of said detection circuit being interconnected to said connectinglines, a bypass line eective to interconnect said switch with one ofsaid connecting` lines when said switch is in said second operativeposition, whereby when said switch is in said first position saidoscillator, said antenna system and said detection circuit are energizedand apply an alternating current signal to said connecting lines, saidsignal being modiiied upon any intrusion into the protected area, andwhereby when said switch is in said second position said oscillator isdeenergized and a direct current signal is applied from said powersource across said connecting lines which signal provides means at theguard unit for supervising said connecting lines, said guard unitcomprising an ultra sensitive balanced arm relay circuit energized fromsaid connecting lines, an alarm indicator energized in response to theactuation of said balanced arm relay, and indicating means responsive tocurrent iiow through said connecting lines, the current change occurringupon shifting of said switch from one position to another being ofsui'licient magnitude to actuate said balanced arm relay.

3. An alarm system comprising a control unit disposed iu the area to beprotected, a guard unit disposed in an area remote from the protectedvarea, and two connecting lines electrically interconnecting said guardunit and said control unit, said control unit comprising a directcurrent power source, an oscillator circuit, a man ually operated switchhaving first and second operative positions, said switch when in saidrst position being effective to interconnect said power source and saidoscillator circuit, an antenna system connected to said oscillatorcircuit, an antenna tuning circuit connected with said antenna system, adetection circuit interconnected with said antenna system, the outputleads of said detection circuit being interconnected to said connectinglines, a bypass line eiective to interconnect said switch with one ofsaid connecting lines when Vsaid switch is in said second operativeposition, whereby when said switch is in said first position saidoscillator, said tenna system and said detection circuit are energizedand apply an alternating current signal to said connecting lines, saidsignal being modified upon any intrusion into the protected area, andwhereby when said switch is in said second position said oscillator isdeenergized and a direct current signal is applied from said powersource across said connecting lines which signal provides means at theguard unit for supervising said connecting lines, said guard unitcomprising an ultra sensitive balanced arm relay circuit energized fromsaid connecting lines, an alarm indicator energized in response to theaction of said balanced arm relay, and indicating means responsive tocurrent iiow through said connecting lines, said last named meanscomprising a meter, a resistance in said bypass line edective to limitthe current flow through said line to the same order of magnitude as thenormal current output of said detector, whereby said meter is effectiveto provide a current reading with said switch in either said first orsecond positions.

r4. An alarm system comprising a control unit disposed in the area to beprotected, a guard unit disposed in an area remote from the protectedarea, and two connecting lines electrically interconnecting said guardunit and said control unit, said control unit comprising a housingenclosing a direct current power source, an oscillator circuit, amanually operated switch having first and second operative positions,said switch when in said Iiirst position being eifective to interconnectsaid power source and Vsaid oscil-lator circuit, an antenna systemconnected to lsaid oscillator circuit, an antenna tuning circuitconnected with said antenna system, a detection circuit interconnectedwith said antenna system, the output leads of said detection circuitbeing interconnected to said connecting lines, a normally closed tamperswitch mounted within said housing, said switch having con* tacts in oneof said output lines and being adapted to open upon opening of saidhousing, `a bypass line effective to interconnect said switch with oneof said connecting lines when said switch is in said second operativeposition, whereby when said switch is in said iirst position saidoscillator, said antenna system and said detection circuit are energizedand apply an alternating current signal to said connecting lines, saidsignal being modiiied upon any intrusion into the protected area, andwhereby when said switch is in said second position said oscillator isdeenergized and a direct current signal is applied from `said powersource across said connecting lines which signal provides means at theguard unit for supervising said connecting lines, said guard unitcomprising an ultrasensitive balanced ann relay circuit energized fromsaid connecting lines, an alarm indicator energized in response to theactuation of said balanced arm relay, and indicating means responsive tocurrent ow through said connecting lines.

5. An alarm system comprising a control unit disposed in the area to beprotected, a guard unit disposed in an area remote from the protectedarea, and two connecting lines electrically interconnecting said guardunit and said control unit, said control unit comprising a directcurrent power source, an oscillator circuit, a manually operated switchhaving iirst land second operative positions, said switch when in saidrst position being effective to interconnect said power source and saidoscillator circuit, an antenna system connected to said oscillatorcircuit, an antenna tuning circuit connected with said antenna system, adetection circuit interconnected with said antenna system, the outputAleads of said detection circuit being interconnected to said connectinglines, a meter in one of said output leads, a bypass line 'effective tointerconnect said switch with one or said connecting lines when saidswitch is in said second operative position, whereby when said switch isin said iii-st position said oscillator, said antenna system and saiddetection circuit are energized and apply an alternating current signalto said connecting lines, said signal being modied upon any intrusioninto the protected area, and whereby when said switch is in said secondposition said oscillator is deenergized and a direct current signal isapplied trom said power source across said connecting lines which signalprovides means at the guard unit for supervising said connecting lines,said guard unit comprising an ultrasensitive balanced arm relay circuitenergized from said connecting lines, an alarm indicator energized inresponse to the actuation of said balanced arm relay, and a Ymeterresponsive to current iiow through said indicators.

References Cited in the tile of this patent UNTEDSTATES PATENTS MuehterJ-uly 5, 1960

